The biosynthesis of asparagine-linked glycoproteins utilizes a
dolichyl diphosphate-linked glycosyl donor, which is assembled by the
series of membrane-bound glycosyltransferases that comprise the
dolichol pathway.

Alg2 mannosyltransferase from Saccharomyces cerevisiae carries out an
alpha-1,3-mannosylation of D-Man-beta-(1->4)-D-GlcNAc-beta-(1->4)-D-
GlcNAc-diphosphodolichol, followed by an alpha-1,6-mannosylation (cf.
EC 2.4.1.257), to form the first branched pentasaccharide
intermediate of the dolichol pathway.